Random Java, AWS and Terraform notes

content/docs/programming/java.adoc

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+++++
+
+== Java
+
+=== Class file versions
+
+- Java SE 13 = 57 (0x39 hex)
+- Java SE 12 = 56 (0x38 hex)
+- Java SE 11 = 55 (0x37 hex)
+- Java SE 10 = 54 (0x36 hex)
+- Java SE 9 = 53 (0x35 hex)
+- Java SE 8 = 52 (0x34 hex)
+- Java SE 7 = 51 (0x33 hex)
+- Java SE 6.0 = 50 (0x32 hex)
+- Java SE 5.0 = 49 (0x31 hex)
+- JDK 1.4 = 48 (0x30 hex)
+- JDK 1.3 = 47 (0x2F hex)
+- JDK 1.2 = 46 (0x2E hex)
+- JDK 1.1 = 45 (0x2D hex)

content/docs/software/terraform.adoc

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+
+== Terraform
+
+https://www.terraform.io/[Terraform] by HashiCorp is a tool to provision and modify
+infrastructure via declarative config files.
+
+=== Notes
+
+* An `azurerm_virtual_machine` can't be recreated out-of-the-box as the OS disk
+  will still exist. The option `delete_os_disk_on_termination` will delete the
+  disk when the machine terminates, which keeps everything happy.
+* After adding new providers you need to re-run `terraform init` to install them.
+* To force recreation of a resource you can taint it, e.g.
+  `terraform taint azurerm_virtual_machine.mymachine`

content/docs/technologies/aws.adoc

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+title = "AWS"
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+
+== AWS
+
+=== EC2
+
+* Amazon Linux is based on RHEL, so uses the `yum` package manager
+* The default user is `ec2-user`